DFB laser diode having a lateral coupling for large output power

Abstract

The invention relates to a DFB laser diode having a lateral coupling, which comprises at least one semi-conductor substrate ( 10 ), at least one active layer ( 40 ) that is arranged on the semiconductor substrate, at least one ridge ( 70 ) that is arranged above the active layer ( 40 ), at least one periodic surface structure ( 110 ) that is arranged next to the ridge ( 70 ) above the active layer ( 40 ) and at least one wave guide layer ( 30, 50 ) comprising a thickness ≧1 μm that is arranged below and/or above the active layer.

The invention claimed is: 
     
       1. A distributed feedback (DFB) laser diode having a lateral coupling, comprising:
 at least one semiconductor substrate; 
 at least one active layer that is arranged on the semiconductor substrate, wherein a cross section of the at least one ridge is tapered in the direction of at least one laser mirror, wherein a width of the at least one ridge is tapered in the direction of both laser mirrors, and wherein the tapering of the width of the at least one ridge in the direction of both laser mirrors is asymmetrical with respect to a longitudinal and/or a lateral direction; 
 at least one ridge that is arranged above the active layer; 
 at least one periodic surface structure that is arranged above the active layer next to the at least one ridge, wherein the periodic surface structure is applied to an upper cladding layer that remains after an etching process; and 
 at least one wave guide layer that is arranged below and above the active layer, wherein a lower wave guide layer of the at least one wave guide layer comprises a thickness in the range of 1 μm to 5 μm. 
 
     
     
       2. The DFB laser diode of  claim 1 , wherein the lower wave guide layer comprises a thickness in the range of 1.5 μm to 3 μm. 
     
     
       3. The DFB laser diode of  claim 1 , wherein the lower wave guide layer comprises a thickness in the range of 2.0 μm to 2.5 μm. 
     
     
       4. The DFB laser diode of  claim 1 , wherein an upper wave guide layer of the at least one wave guide layer comprises a thickness in the range of 15 nm to 100 nm. 
     
     
       5. The DFB laser diode of  claim 1 , wherein an upper wave guide layer of the at least one wave guide layer comprises a thickness in the range of 20 nm to 50 nm. 
     
     
       6. The DFB laser diode of  claim 1 , wherein the difference of the refractive indices between the active layer and the at least one wave guide layer is in the range from 0.04 to 0.40. 
     
     
       7. The DFB laser diode of  claim 1 , wherein the difference of the refractive indices between the active layer and the at least one wave guide layer is in the range from 0.06 to 0.30. 
     
     
       8. The DFB laser diode of  claim 1 , wherein the difference of the refractive indices between the active layer and the at least one wave guide layer is in the range from 0.08 to 0.25. 
     
     
       9. The DFB laser diode of  claim 1 , wherein the refractive index of the at least one wave guide layer remains constant over the thickness of the layer. 
     
     
       10. The DFB laser diode of  claim 1 , wherein the refractive index of the at least one wave guide layer changes over the thickness of the layer in a linear manner. 
     
     
       11. The DFB laser diode of  claim 1 , wherein a width of the at least one ridge is linearly tapered in the direction of at least one laser mirror. 
     
     
       12. The DFB laser diode of  claim 1 , wherein a width of the at least one ridge is exponentially tapered in the direction of at least one laser mirror. 
     
     
       13. The DFB laser diode of  claim 1 , wherein the at least one ridge comprises a width in the range from 0.5 μm to 10 μm. 
     
     
       14. The DFB laser diode of  claim 1 , wherein the at least one ridge comprises a width in the range from 2 μm to 7 μm. 
     
     
       15. The DFB laser diode of  claim 1 , wherein the at least one ridge comprises a width in the range from 2 μm to 4 μm. 
     
     
       16. The DFB laser diode of  claim 1 , wherein a width of the at least one ridge on at least one laser mirror is in the range from 100 nm to 700 nm. 
     
     
       17. The DFB laser diode of  claim 1 , wherein a width of the at least one ridge on at least one laser mirror is in the range from 200 nm to 500 nm. 
     
     
       18. The DFB laser diode of  claim 1 , wherein the tapering of the width of the at least one ridge in the direction of at least one laser mirror occurs over a length in the range from 50 μm to 1000 μm. 
     
     
       19. The DFB laser diode of  claim 1 , wherein the tapering of the width of the at least one ridge in the direction of at least one laser mirror occurs over a length in the range from 100 μm to 600 μm. 
     
     
       20. The DFB laser diode of  claim 1 , wherein the tapering of the width of the at least one ridge in the direction of at least one laser mirror occurs over a length in the range from 200 μm to 400 μm. 
     
     
       21. The DFB laser diode of  claim 1 , wherein the periodic surface structure does not extend along the area where the cross-section of the at least one ridge changes. 
     
     
       22. The DFB laser diode of  claim 1 , further comprising:
 an additional layer that is arranged in the at least one ridge and which has a refractive index larger than the refractive index of the at least one ridge. 
 
     
     
       23. The DFB laser diode of  claim 22 , wherein the additional layer with the high refractive index is arranged above the periodic surface structure. 
     
     
       24. The DFB laser diode of  claim 22 , wherein the difference of refractive indices between the additional layer with high refractive index and the at least one ridge is in the range from 0.10 to 0.40. 
     
     
       25. The DFB laser diode of  claim 22 , wherein the difference of refractive indices between the additional layer with high refractive index and the at least one ridge is in the range from 0.15 to 0.35. 
     
     
       26. The DFB laser diode of  claim 22 , wherein the difference of refractive indices between the additional layer with high refractive index and the at least one ridge is in the range from 0.20 to 0.30. 
     
     
       27. The DFB laser diode of one of the  claim 22 , wherein the thickness of the additional layer with high refractive index is in the range ≦5% of a thickness of the at least one ridge.